In the context of service architectures based on Internet protocol (IP) multimedia subsystem (IMS) architectures or on a session initiation protocol (SIP) core, when a user desires to receive a multimedia message on a plurality of terminals, the messaging server transfers the invitation to set up a session to each of the terminals. However the communications session is established with only one of the terminals: specifically, the first of the terminals to respond positively to the invitation (by a message of the 200 OK type). Consequently, the user can make use of only one of the terminals during the session.
In the push-to-talk context (an IP mobile conference) as described in particular by US 2007/0129051, a session is set up with a group of users by generating an invitation to set up a session that includes the identifier of the group. The method described does not make provision for being able to contact a given user over more than one of that user's terminals.